This invention relates to busway electrical distribution systems and more specifically to structural housing supports for busway devices.
Busway electrical distribution systems are well known in the art of electrical distribution. Busway systems are comprised of a number of factory assembled sections each including a number of individually insulated generally flat electrical conductors or busbars stacked one upon another and enclosed within a housing which provides protection and support for the busbars. Each housing includes a duct top and a duct bottom which cover the flat surfaces of the bus bars and two duct sides which cover the edges of the bus bars. The duct tops and bottoms can be made of electrically conductive material such as aluminum or copper for carrying the system ground current. The duct sides are generally made of steel formed to provide strength to the housing. The housing is generally held together by screws and nuts, rivets, stitching or other similar methods. The width of the enclosure is determined by the width of the busbars and the number of busbar stacks enclosed within the housing. During a short circuit, magnetic forces around the busbars tend to push the busbars away from each other, thereby causing the tops and bottoms to bulge. High short circuits can cause the housing to be pulled apart. To prevent or limit short circuit damage surge clamps are placed across the duct tops and bottoms at each end of the busway section and at predetermined intervals between the ends. The surge clamps are generally U-shaped in cross-section with flanges closing the ends and formed from 12 Ga. or 14 Ga. sheet or strip steel. The surge clamps are fastened to the duct sides by means such as screws which pass through the duct side and into the surge clamp end flanges. The length of the surge clamp is determined by the width of the busway enclosure on which it is to be used. Since there are a number of enclosure widths, there must also be a like number of surge clamp lengths. Therefore, large quantities of each surge clamp length must be made and stored in inventory to maintain an adequate supply for production line usage. Manufacturing of surge clamps requires shearing blanks for each required length, forming each blank into a surge clamp, painting the formed surge clamp with an acceptable corrosion resistant coating and placing the finished surge clamps, sorted by length (or part number), into inventory. In some cases the end and side flanges are welded together to give additional strength to the surge clamp. This is a time consuming process, and since at least four surge clamps are required for each busway section, large quantities of each surge clamp length are manufactured at one time and placed in inventory to prevent a busway production line stoppage due to shortages of a particular surge clamp. Also, having to maintain a large inventory of parts is expensive since it requires manufacturing time to make the surge clamps and storage space to store the surge clamps until needed. It would therefore be desirable to have surge clamps which can be manufactured in minutes as needed from a common rawstock, thus eliminating the need for an extensive manufacturing process and a large inventory of many different parts.
The surge clamps of the present invention can be manufactured as required in a matter of minutes on or near the busway assembly line thereby eliminating the blank shearing, forming, painting and storing of finished parts. An extruded surge clamp rawstock is provided in lengths easily handled by one person. Each surge clamp is made by cutting the surge clamp rawstock off at the required surge clamp length by using a shearing die or an abrasive cutoff saw. Thus the only inventory requirement is for the extruded rawstock which is used for all surge clamp lengths. The surge clamp rawstock is preferably a corrosion resistant material such as aluminum and therefore requires no additional corrosion protection.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.